In general, a PDP comprises two opposed glass substrates, a pair of electrodes systematically arranged in the glass substrates, and a gas (mainly Ne or the like) sealed therebetween. A voltage is applied across the electrodes to produce discharge within minute cells around the electrodes to emit light from each cell, thereby displaying information. Systematically arranged cells are selectively subjected to discharge luminescence in order to display information. Such PDPs are classified into two types, a direct current type PDP, wherein electrodes are exposed to a discharge space (DC type), and an alternating current type (AC type) wherein electrodes are covered with an insulating layer. Each of these types is further classified into a refresh drive system and a memory drive system according to display functions and drive systems.
FIG. 7 is an embodiment of the construction of an AC type PDP. In the drawing, a front plate 71 and a back plate 72 are shown separately from each other. As shown in the drawing, the glass front plate 71 and the back plate 72 are arranged parallel and opposite to each other. Barrier ribs 73 are provided so as to stand in a fixed state on the back plate 72 in its front surface side, and the front plate 71 and the back plate 72 are held while leaving a given distance between the front plate 71 and the back plate 72 by means of the barrier ribs 73. Composite electrodes each comprising a sustaining electrode 74 as a transparent electrode and a bus electrode 75 as a metallic electrode are provided parallel to each other on the front plate 71 in its back plate side, and a dielectric layer 76 is provided so as to cover the composite electrode. Further, a protective layer 77 (MgO layer) is provided on the surface of the dielectric layer 76.
On the other hand, address electrodes 78 are provided between the barrier ribs 73 on the back plate 72 in its front surface side so that the address electrodes 78 are parallel to each other and orthogonal to the composite electrodes. Further, a fluorescent substance 79 is provided so as to cover the wall surface of the barrier ribs 73 and the bottom face of cells.
In the AC type PDP, a predetermined voltage is applied, from an alternating-current power supply, across the composite electrodes on the front plate 71 to create an electric field, thereby producing discharge in each cell as a display element defined by the front plate 71, the back plate 72, and the barrier ribs 73. Ultraviolet light produced by the discharge permits the fluorescent substance 79 to emit light, and light passed through the front plate 71 is viewed by an observer.
Use of a photosensitive resin film constituted by a fluorescent substance-containing photosensitive resin layer has been proposed for coating the fluorescent substance (see, for example, Japanese Patent Laid-Open Publication Nos. 273925/1994, 95239/1996, and 95250/1996).
In this coating method, a photosensitive resin layer is pressed into cells formed in a back plate of a PDP, the photosensitive resin layer is then exposed and developed, followed by firing to burn off the organic material in the photosensitive resin layer, thereby forming a fluorescent substance layer on the surface of the cells. In this case, a satisfactorily large discharge space should be ensured in the cells after the firing, making it necessary to increase the content of the organic material in the photosensitive resin layer, that is, to lower the content of the fluorescent substance. This operation requires a large quantity of thermal energy for firing and further poses an additional problem that the firing evolves a large amount of decomposition gas, rendering the control of the firing oven complicated.
Further, the above method involves a serious problem that, since the photosensitive resin layer pressed into the cells contains a large amount of the organic material, the photosensitive resin layer shrinks with the elapse of the firing time and the finally formed fluorescent substance layer lifts from the cell surface and does not come into intimate contact with the cell surface.
In the above method, the step of exposure and development, that is, wet treatment, is indispensable for the formation of a patterned fluorescent substance layer in cells provided between adjacent barrier ribs. This renders the process complicated. Further, a developable resin, particularly an alkali-developable photosensitive resin, should always be used as the photosensitive resin. It is difficult to select a photosensitive resin that can be fully burned off.
Further, at the time of development, when the adhesion of the fluorescent substance-containing layer to the wall surface of the ribs is low, the fluorescent substance-containing layer is likely to be separated from the wall surface of the ribs. Development conditions should be optimized for the prevention of the separation.
Accordingly, an object of the present invention is to solve the problems of the prior art and to provide a photosensitive resin film that can eliminate the step of development and the like, realizing a simplified process, and in addition can form an even fluorescent substance layer in intimate contact with the cell surface, and a process for producing a back plate of PDP using the film.